A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. comprising part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
Immersion lithography has become an important lithographic imaging technique. In immersion lithography, a liquid is provided between an optical imaging system and a target portion of the substrate to be illuminated by the optical imaging system. This liquid provides a way to further increase the numerical aperture of the optical imaging system, which may result in enhanced imaging performance. A variety of systems and apparatus have been proposed to implement the immersion lithography technique. One of the challenges that is posed on these systems is to handle the liquid as the liquid may contribute to contamination and/or degradation of lithographic apparatus elements. Furthermore, the presence of liquid on a substrate may pose a problem in terms of temperature control since liquid may evaporate thus resulting in local cooling of the substrate. Local cooling may be problematic in keeping stable mechanical conditions of the substrate so that substrate may be accurately aligned for proper imaging.